A report by the government’s Office of Rail and Road revealed that stress corrosion was a primary cause for over 180 trains developing cracking so severe they needed to be withdrawn from service.
The interim report, published after the withdrawal of the Hitachi Class 800 and 385 series of trains, following cracks being found near the anti-roll bar fixing points, the yaw damper bracket and the area where lifting plates attach to the body in May.
The first two cracks were discovered to have been caused by fatigue, where the forces pressed against them as a result of the high speeds they travel cause the parts to fail earlier than expected.
The second, however, was caused by stress corrosion cracking, a particular corrosion control issue where a material that is subject to pressure and strong forces then also is exposed to a corrosive substance, causing quicker cracking than otherwise expected.
This caused the trains to be quickly removed from service whilst the report was drafted and research was undertaken to ascertain just what was causing the cracking, with several of the trains being returned to service after finding them to be safe.
The ORR found that the train operators with trains affected provided clear information to passengers affected by the disruption.
The final report, expected this December, will establish the root cause of the stress corrosion cracking, why it affected Hitachi’s trains specifically, as well as their plans for long term fleet management and recovery.
It will also highlight the lessons the rail industry can learn about the importance of protecting their trains from corrosion, as a particular failure could have potentially dire circumstances.